LOUISVILLE, Ky. (AP) — For Rory McIlroy, the shockingly bad shot came out of nowhere.
By the time he walked off the 18th green, there was little doubt he was still the man to beat at the PGA Championship.
McIlroy ripped off four straight birdies on the back side and closed with another at the 18th hole, shooting a 5-under 66 at Valhalla that left him one shot off the lead Thursday.
Coming off wins at the British Open and Firestone, McIlroy came into the final major of the year as an overwhelming favorite. Even with a major blunder at the 10th, where he knocked his second shot over a fence and took double bogey, he was right on the heels of Lee Westwood, Ryan Palmer and Kevin Chappell.
"I'm really happy with everything," McIlroy said. "I've got a good thing going right now. I'm trying to ride that momentum as much as I can."
Then there's Tiger Woods, who can't seem to get anything going.
Playing just four days after his back flared up at Firestone, forcing him to withdraw, Woods proclaimed himself fit but sprayed shots all over the course on the way to a 74 that left him tied for 111th late in the day.
"That wasn't very good," said Woods, who made only one birdie — and had to hole out from the fairway to do that. "A lot of bad shots."
One landed in a creek. Another sent the gallery scrambling. Yet another rolled into a fenced-off area where fans can use cellphones, a good 30 yards right of the fairway.
Too bad Woods couldn't call for help.
"I didn't play as well as I wanted to. I didn't get a putt to the hole," he said. "That's not a good combo."
McIlroy was cruising along when he got to the 10th, having made three birdies on the front side. After putting his tee shot right in the middle of the fairway at the par-5 hole, he yanked the next one out of bounds. A man talking on his cellphone along the fence, not concerned at all with getting in the way, was stunned with he looked up to see a ball sailing over his head.
Especially when he learned whose ball it was.
"I was really annoyed," McIlroy said. "That second shot at 10 is the worst shot I've hit in weeks. It came out of the blue."
He took a penalty and a drop and missed the fairway with his next attempt as well, resulting in a 7. Still shaken by that miscue, McIlroy made bogey at No. 11 to slip to even on the day.
Just like that, he pulled himself together.
Four straight birdies pushed McIlroy right back up the leaderboard, and it could have easily been five in a row. A 12-footer slid over the edge of the cup at the 16th.
At the final hole, McIlroy reached the green in two for an eagle try to share the lead. If curled off at the end, leaving him with a tap-in — his eighth birdie of the round.
"It could have been better," he said. "But a 66 the first day, that's a solid start."
Westwood matched his best round ever at a major, making nine birdies as he carried over the momentum from a closing 63 at Firestone. The 41-year-old Englishman also had a double bogey on his 10th hole of day — at No. 1, after starting on the back — but closed with four straight birdies.
"The golf course was all there in front of me. I just play it as I see it," said Westwood, who has had numerous close calls but never won a major championship. "Last week, I felt like I turned a corner."
Chappell, a 28-year-old Californian in his fourth year on the PGA Tour, turned in a bogey-free round. The final major of the year has produced some unlikely champions — remember Shaun Micheel? — and Chappell hopes to be the latest.
"I can't complain about being in the lead of any golf tournament," said Chappell, whose only professional win came on the Web.com Tour in 2010. "I just look forward to keeping it rolling."
Palmer birdied five of the nine holes on the back side, which is where he started his round. He said the greens were more inviting than he expected.
"I was surprised how soft they were," he said. "It was a pretty easy, relaxing nine for me."
McIlroy was joined at 65 by Jim Furyk, Henrik Stenson, Edoardo Molinari and Chris Wood.
For Furyk, it was another strong start in a tournament he nearly won a year ago. He took a lead to the final day at Oak Hill, only to lose to Jason Dufner by two strokes.
Dufner's title defense lasted only 10 holes. Plagued by a sore neck, he withdrew after a triple-bogey left his score at 8 over, probably ending his Ryder Cup hopes as well. He came in ranked No. 8 in the standings and hoping to somehow play well enough to stay in one of the nine qualifying spots.
"I tried to do what I could to be able to compete some and give it a go," Dufner said, "but it is just pointless."